You are what you eat—and during your pregnancy, so is your baby. But that doesn’t mean you have to double your calories—instead, it’s about filling your diet with balanced nutrition to keep you and your baby healthy and strong. Here’s the scoop on what to eat when pregnant to help your baby grow and develop, plus the smart way to gain weight.

What to eat when pregnant

During pregnancy, your body works to suck every last calorie and nutrient out of your food to provide nourishment for your baby, says Melinda Johnson, director of the Didactic Program in Dietetics at Arizona State University and a spokesperson of the Academy of Nutrition and Dietetics. And since each food group offers different types of nutrients, variety is key. You’ll get calcium, vitamin D and protein from low-fat fairy; vitamin C, minerals, and fiber from fruits and vegetables; fiber and B vitamins from whole grains; plus protein and zinc from lean proteins. In general, it’s a good idea to get at least three different food groups at each meal and two food groups at each snack.

How much weight should I gain while pregnant?

That depends on your pre-pregnancy weight. Women who were underweight before they became pregnant should gain 28 to 40 pounds; average-weight women should gain 25 to 30 pounds; overweight women should gain 15 to 25 pounds; and obese weight should gain 11 to 20 pounds.

And perhaps surprisingly, you aren’t supposed to gain the weight steadily throughout your pregnancy. Since your baby is so tiny during your first trimester, you need only put on about three pounds. But even then, nutrients like folic acid are essential for development, so be sure to eat plenty of foods rich in the vitamin, like lentils and leafy greens (or talk to your doctor about a supplement). And don’t worry too much if you’re feeling queasy: As long as you’re not vomiting for more than a week straight and continue to take your prenatal vitamin, you’re in the clear. (Call your doctor if the vomiting continues, and find morning sickness remedies here.)

During your second and third trimesters, most women need to gain about a pound a week, which you can do by working in an extra 300-calorie snack. But that doesn’t mean those calories should come from just anywhere: When planning what to eat when pregnant, you want the extra energy to come from nutrient-rich foods, like whole grain cereal with low-fat milk, low-fat cottage cheese with pineapple chunks, or a slice of whole wheat toast with peanut butter and banana, says Johnson.